Changes in diatom, pollen, and chironomid assemblages in response to a recent volcanic event in Lake Galletué (Chilean Andes)

Abstract

Several lakes in Chile are near important volcanic areas where eruption impacts can limit the quality of lacustrine sediments for reconstructing past environmental changes. In this study, we report changes in diatoms, pollen, and chironomids assemblages after a tephra deposition in Lake Galletue´(Chilean Andes). A sediment core obtained from Lake Galletue´(40 m water depth) was sliced in 1 cm intervals and subsamples were taken to analyze each proxy. 210 Pb and 137 Cs activities were measured to obtain the geochronology and mineralogical analyses were performed to determine the mineral composition of the tephra. Diatom species composition and productivity were modified when the lake received the tephra; Aulacoseira granulata decreased and was later replaced by Cyclotella af. glomerata. After the tephra input, Aulacoseira granulata abundance increased to pre-disturbance levels and Cyclotella af. glomerata decreased. These changes seem to suggest a momentary increase in lake nutrient levels after the tephra deposition. Chironomid assemblages also decreased in head capsules just after the tephra deposition, but the most important change was the replacement of Ablabesmyia by Parakiefferiella, probably due to the sedimentological changes produced by the input of coarse tephra grains. Furthermore, unlike other studies, chironomid assemblages in Lake Galletue´did not show a decrease drastically in diversity within the tephra layer. The pollen analysis indicated that, prior to the volcanic event, the vegetal community was dominated by Nothofagus sp., Araucaria araucana, and Blechnum sp.-type. After the tephra deposition, the same taxa are dominant, indicating that the volcanic event seems not produce changes in the vegetation. Nevertheless, within the tephra layer it is possible to see an increase in Poaceae, which represent -due to the percolation process -the effect of eruption on the vegetation. According to our results, diatoms were the most sensitive proxy for describing the changes produced by tephra deposition into the aquatic ARTICLE IN PRESS www.elsevier.de/limno 0075-9511/$ -see front matter (R. Urrutia).ecosystem and, despite the noticeable changes in its sedimentological properties; the lake seems to have a high resilience capacity, allowing it to return to pre-tephra input conditions.

Assessing the effects of climate and volcanism on diatom and chironomid assemblages in an Andean lake near Quito, Ecuador

“…Changes to the diversity and abundance of diatom and chironomid assemblages following tephra deposits have been recorded elsewhere in the Andes (Urrutia et al, 2007;Massaferro and Corley 1998). In Laguna Baños, Cocconeis placentula records the single largest change in species relative abundance (>20%) between adjacent intervals (Fig.…”

“…Rather, immediately above the tephra layer, chironomid head capsules were absent and abundances remained low until 20-cm depth. A decrease in the concentration of head capsules following a tephra deposit was recorded in Andean lakes from Chile and Argentina (Urrutia et al, 2007;Massaferro and Corley 1998). This drop in abundance in the sediments following the tephra may be due to disruptions to chironomid habitat and food supply.…”

“…In addition to metals and other elements, volcanic events can impact aquatic ecosystems by altering limnological properties including turbidity and light regimes, pH, silica, nutrients, and salinity (Barker et al, 2000, Blong 1984). Changes to the diversity and abundance of diatom and chironomid assemblages following tephra deposits have been documented in mountain lakes in British Columbia, Canada (Hickman and Reasoner 1994), Mexico (Telford et al, 2004), as well as in the Andes (Urrutia et al, 2007;Massaferro and Corley 1998). In volcanically active regions, such as the northern portion of the Ecuadorian Andes, tephras may be important agents of change to aquatic ecosystems.…”

Differential resilience of ancient sister lakes Ohrid and Prespa to environmental disturbances during the Late Pleistocene

“…It has been suggested that the interaction of volcanic ash deposition with a receiving lake triggers perturbations, primarily through the effect of tephra weathering but also through changes in pH, mineral concentration, organic matter input, and short-term light deprivation (e.g., Harper et al, 1986;Barker et al, 2003;Telford et al, 2004;Cruces et al, 2006;Urrutia et al, 2007;D'Addabbo et al, 2015). Depending on the magnitude of the disturbance and the resilience of the respective ecosystem (i.e., the amount of disturbance an ecosystem can tolerate without changing its regime; Holling et al, 1973Holling et al, , 1986Scheffer and Carpenter, 2003;Baho et al, 2014), lake biota may react with extinction events and/or changes in community structures and functions.…”

Post-glacial diatom-inferred aquatic changes in Sicamous Creek Lake, British Columbia, Canada

“…Confounding events of ecoclimatic diatom assemblages may be rare, but significantly large, volcanic tephra influx has affected diatom community relative abundance and composition in lakes elsewhere (BARKER et al, 2000, 2003, BARSDATE and DUGDALE, 1972, BERTRAND et al, 2005, BIRKS and LOTTER, 1994, CRUCES et al, 2006, KILIAN et al, 2006, LOTTER et al, 1995, TELFORD et al, 1999, 2004, URRUTIA et al, 2007, VOLLAND 2006, WISSMAR et. al., 1982.…”